This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This is an open-label, single-arm, multi-cohort, multicenter, and two-stage, Phase 2 study of R1507 for the treatment of patients with recurrent or refractory sarcoma. Five cohorts of sarcoma patients defined by histopathologic classification will be studied in parallel: (1)Ewing's sarcoma (Ewing's family of tumors), (2) osteosarcoma, (3) synovial sarcoma, (4)rhabdomyosarcoma and (5) other sarcomas of the following subtypes: alveolar soft part sarcoma, desmoplastic small round cell tumor, extraskeletal myxoid chondrosarcoma, clear cell sarcoma, and myxoid liposarcoma. All subjects receive R1507 at a dose of 9 mg/kg once weekly until disease progression, unacceptable adverse event, withdrawal or death. Up to 245 evaluable subjects will be enrolled. In order to allow for some patients who may be invaluable (approximately 5%), a total of 68 patients with Ewing's sarcoma (primary cohort), 37 patients for the non-primary ESFT cohort and the other 3 sarcoma subtypes and 42 _other_ sarcomas will be recruited. R1507 will have an anti-tumor effect on patients with recurrent or refractory sarcoma. 1. To determine the overall objective response rate of R1507 in patients with recurrent or refractory osteosarcoma, synovial sarcoma, rhabdomyosarcoma and other sarcomas of the following subtypes: alveolar soft part sarcoma, desmoplastic small round cell tumor, extraskeletal myxoid chondrosarcoma, clear cell sarcoma, and myxoid liposarcoma. 2. To determine the progression-free survival at 18 weeks from start of treatment of patients with progressive, recurrent or refractory Ewing's sarcoma (Ewing's family of tumors) treated with R1507. 1. To estimate the duration of response, progression-free survival rate at 18 weeks from start of treatment and overall progression-free survival of patients with recurrent or refractory, osteosarcoma, synovial sarcoma, rhabdomyosarcoma and other sarcomas of the following subtypes: alveolar soft part sarcoma, desmoplastic small round cell tumor, extraskeletal myxoid chondrosarcoma, clear cell sarcoma, and myxoid liposarcoma who were treated with R1507. 2. To determine the overall objective response rate, response duration, overall progression-free survival and overall survival of patients with progressive, recurrent or refractory Ewing's sarcoma (Ewing's family of tumors) treated with R1507. 3. To define the population pharmacokinetic profile of R1507 in selected study patients. 4. To define the tolerability and adverse event profile of R1507 in sarcoma patients.